Cryosurgical instrument

ABSTRACT

A cryosurgical instrument includes a feed line for conveying fluid into an expansion chamber. The feed line has a capillary line section that terminates in the expansion chamber and forms an aperture for the fluid to undergo the Joule-Thomson effect. The flow cross-section of the feed line decreases in at least one transition section of the feed line in the form of a funnel. Following each transition section there preferably follows a step section, in which latter section the flow cross-section is preferably largely constant. The last step section is preferably formed by the capillary line section. Due to the acceleration of the fluid in the transition sections and the abating of pressure fluctuations in the capillary tube section and, optionally in the additional step sections, the expansion range in the expansion chamber is increased, without impeding the backflow of the expanded gas out of the expansion chamber.

RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.16/051,902, filed Aug. 1, 2018, which claims the benefit of EuropeanPatent Application No. 17184993.8, filed Aug. 4, 2017, the contents ofeach application being incorporated herein by reference as if fullyrewritten herein.

TECHNICAL FIELD

The invention relates to a cryosurgical instrument that operates underutilization of the Joule-Thomson effect.

BACKGROUND

Prior art has disclosed medical instruments whose working end is beingcooled in order to thus generate physiological or therapeutic effects onthe tissue of the patient. For example, from publication WO 02/02026 A1there is known a cryoprobe that comprises a tip for cutting, in whichcase liquid cooling means is supplied to the tip in order to cool saidtip. Publication U.S. Pat. No. 6,830,581 B2 describes a heat transferelement to be inserted into a blood vessel, in which case said elementis to cool blood in the vessel in that cooled working agent is suppliedto the tip of the instrument.

Instruments for cryosurgery work, for example, with the targetedutilization of the Joule-Thomson effect, in which case a fluidexperiences a reduction of its temperature due to being slowed down.

Publication DE 10 2008 024 946 A1, for example, discloses a cryosurgicalinstrument that comprises a feed line for feeding a fluid, in particulara gas, into an expansion chamber in the head of the probe. On the frontside of the feed line there is an aperture with an opening through whichthe fluid flows out of the feed line into the expansion chamber and isthus expanded, whereby the fluid cools. In doing so, the probe tip iscooled. The cooled fluid flows from the probe tip back through a gasfeedback line.

Publication WO 2006/006986 A2 describes a cryosurgical instrumentcomprising a tube with a closed end. Arranged inside the tube there is agas feed line, to the end of which a capillary tube is connected, inwhich case the end of the latter terminates in an expansion chamber inthe tip of the probe.

Publication US 2012/0 130 359 A1 describes an instrument for cryotherapywith the use of which nerves at the operating site can be affected withcold for therapeutic purposes. The instrument comprises a shaft, at theend of which a working section is provided. Extending through the shaftin the working section, there is a feed line for feeding coolant backinto the working section. At the end of the feed line, there may beprovided an aperture or a capillary tube with which the feed lineterminates in an expansion chamber in the working region.

Publication US 2005/0 016 188 A1 describes an instrument for thecryosurgical ablation of tissue with a cryocatheter comprising a tubehaving a closed distal end, wherein a feedback line extends in the tubeup to the end of the instrument, in which case a capillary tube isarranged in the end of the feed line, said capillary tube terminating ina chamber on the distal end of the instrument.

SUMMARY

It is the object of the present invention to state an improvedcryosurgical instrument.

This object is achieved with a cryosurgical instrument described hereinthat, for example, may be disposed for taking a tissue sample. Thecryosurgical instrument according to the invention comprises a feed linefor supplying a working fluid, in particular a gas, into an expansionchamber that is preferably arranged on the distal end of the instrument.The feed line has a capillary line section that terminates in theexpansion chamber. A return arrangement for returning gas from theexpansion chamber is connected to the expansion chamber. The feed linehas at least one first section and one second section that form linesections displaying different-size inside cross sections (insidecross-sectional areas). The inside cross-sections determine the flowcross-section for the fluid through the feed line in the first and thesecond sections. The feed line of the instrument according to theinvention is designed in such a manner that the path of flow of thefluid through the feed line tapers in a transition section of the feedline from the first section to the second section in a funnel-shapedmanner in the direction toward the expansion chamber. With thisfunnel-like tapering of the inside cross-section of the feed line in thetransition section, it is possible to achieve a stepped progression ofthe flow cross-section along the feed line with a decrease of the insidecross-section, said decrease being preferably continuous (steady) orstep-by-step. As a result of the fact that the inside cross-section ofthe feed line tapers at least once in a funnel-shaped manner in thedirection of flow of the fluid through the feed line in the directiontoward the expansion chamber, the fluid is accelerated in the at leastone funnel-shaped transition section of the feed line. Due to thefunnel-shaped tapering in the transition section the flow cross-sectiondoes not decrease suddenly (abruptly) from the flow cross-section of thefirst section toward the flow cross-section of the second section thatis smaller compared to the flow cross-section of the first section.Therefore, due to the funnel shape of the transition-section, pressurefluctuations of the accelerated fluid in the section of the feed linefollowing the funnel-shaped transition section can be largely reduced orprevented.

The instrument according to the invention works, for cooling the workingsection of the instrument, by utilizing the Joule-Thomson effect thatmanifests itself on the fluid when the fluid expands in the expansionchamber. Due to the uniform acceleration in the transition section andthe use of the capillary line section as the distal end section of thefeed line, it is accomplished that the distance over which the fluidparticles remain largely together upon exiting from the mouth openinginto the expansion chamber is lengthened compared to an instrument thatdoes not comprise the described funnel-shaped taper and capillary linesection. In doing so, it can be prevented, in particular, that the jetwill widen excessively after the mouth and thus impede the backflow ofthe gas out of the expansion chamber. As a result of this, theinstrument head that contains the expansion chamber and that may containat least one section of the return system, can be designed in a slimmanner. This smoothes the path to obtain miniaturized instrument heads.The use of the capillary line as aperture for the fluid, as well as thelargely pressure-surge-free acceleration of the fluid in the at leastone transition section in which the flow cross-section tapers in afunnel-shaped manner, in particular, smooth the path to a particularlyslim instrument head with which, for example, a safe tissue sampleremoval can be simplified.

Particularly preferably, the feed line is configured in such a mannerthat the inside cross-section of the feed line tapers in a funnel-shapedmanner in the transition section toward the capillary line section. As aresult of this, the fluid can be accelerated and pressure fluctuation atthe time of entry into capillary line section can be largely reduced orprevented on entry into the capillary line section, this leading to alarge free path length of the fluid, over which length the fluidparticles largely remain together upon leaving the capillary linesection into the expansion chamber. Preferably, the tapering of theinside cross-section is continuous in a transition region that extendsfrom ahead of the transition section toward the capillary linesection—through the transition section and into the capillary linesection. The inside wall surface of the feed line in the transitionregion is preferable free of edges so that, within the transition regionalong the flow path, there do not exist any sudden changes of thegradient of the inside cross-section.

Preferably, the tapering angle with which the inside cross-section ofthe feed line tapers at least in the transition section toward thecapillary line section in a funnel-like manner is 15° at minimum and 40°at maximum. The tapering angle is included by opposing sections of theinside wall surface of the transition section that determines the flowcross-section through the transition section.

The length of the capillary line section is preferably between a minimumof 1 mm and a maximum of 15 mm. The inside diameter of the capillaryline section that determines the flow cross-section of the capillaryline section is preferably between a 60 micrometers at minimum and 200micrometers at maximum.

Preferably, the feed line has at least two transition sections in whichthe flow path through the feed line tapers in a funnel-shaped manner inthe direction of flow toward the expansion chamber.

The first section and the second section preferably form step sectionsof a series of two, three or more than three step sections of the feedline, wherein a transition section is provided between each two stepsections, said transition section being adjacent to the two stepsections. As described, the flow cross-section through the at least onetransition section, preferably in each transition section, decreases asin a funnel in the direction of the mouth opening of the feed linetoward the expansion chamber. The area contents of the insidecross-sectional areas of each step section belong to an insidecross-section step, wherein the area contents of the insidecross-sectional areas of an inside cross-section step of a step sectionarea are greater than the area contents of the inside cross-sectionalareas of the inside cross-section step of the step section adjacent—inthe direction toward the mouth of the capillary line sectiondownstream—to the same transition section. As a result of this, astepped progression of the flow cross-section of the feed line up to themouth of the feed line is provided, in which case the flow path in thetransition sections having the funnel-shaped taper is not reducedabruptly—due to the funnel shape—from one cross-section step to thesubsequent cross-section step, but is preferably reduced continuously orstep-by-step or, in at least one longitudinal section of the transitionsection, continuously and, in at least another longitudinal section ofthe transition section, step-by-step in the direction toward theexpansion chamber and may advantageously remain largely constant in thestep sections along the step sections. The capillary line section mayform the last step section of the sequence in flow direction toward themouth of the last step section. Due to the acceleration in thefunnel-shaped transition sections, the fluid particles are imparted witha high speed that carries the fluid jet—upon exiting from the mouth—farinto the expansion chamber, as a result of which the expansion range ofthe fluid is enlarged and the effectiveness of cooling can be improved.Due to the funnel-like taper and the provided step sections, theacceleration of the fluid in the direction toward the expansionchamber—viewed over the course of the sequence—occurs in steps, therebymaking possible a reduction of pressure surges and turbulences in thefluid. As a result of this, the range of expansion of the gas in thepressure chamber is enlarged.

During the transition from the mouth opening of the capillary sectioninto the expansion chamber, the flow cross-section for the fluidpreferably surges. This promotes a strong formation of the Joule-Thomsoneffect on the expanding fluid. In addition, a section of the expansionchamber may be available as part of the return system.

The feed line is preferably arranged in the return line, and/or thereturn line is arranged, for example, next to the feed line. Theparticularly preferred ratio of the flow cross-section in the returnline next to the capillary line section and/or around the capillary linesection with respect to the inside cross-section of the capillary linesection is greater than or equal to 5.

Preferably, the feed line is configured in such a manner that theoutside cross-section (outside cross-sectional area) of the feed linedoes not decrease abruptly at the funnel-shaped transition sections fromthe outside cross-section of a step section to the outside cross-sectionof the step section adjacent to the same transition section but,preferably, decreases continuously or step-by-step or, in at least onesubsection of the section of the feed line whose outside cross-sectiontapers, step-by-step and, in another subsection of the section,continuously in the direction toward the mouth of the capillary linesection. Viewed in the direction of flow of the gas flowing away fromthe expansion chamber following expansion, the outside cross-section ofthe feed line preferably, accordingly does not increase abruptly but,preferably, continuously and/or step-by-step. If the wall of the feedline, at the same time, forms a wall of the return system, in particulara return line, the return of the gas from the expansion region throughthe space provided by the outside cross-section reduction can beimproved. Different from an abrupt decrease of the outside cross-sectionof the feed line in the direction toward the mouth, the outside diameterof the flow cross-section for the gas that flows back is not changedabruptly; it is, for example, tapered. As a result of this, the flowresistance of the return system, in particular a return line may bedecreased.

The instrument may be configured in such a manner that the flowcross-section of the return line in the direction of flow of the gasduring the return away from the expansion chamber decrease, in thetransition sections, continuously or step-by-step or, in the transitionsections in at least one length section, continuously and, in at leastone other length section, step-by-step.

Preferably, at least the section of the feed line having the capillaryline section and the transition section adjacent to the capillary linesection is configured without seams. This simplifies a reliable processof manufacturing the instrument in order to avoid problems and abruptchanges of the flow cross-section of the feed line up to its mouth.Particularly preferably, at least the section of the feedback linehaving the capillary line section and the funnel-shaped transitionsection is configured in one piece without seam, so that a reliableprocess of producing the transition sections and the capillary linesection is simplified.

Overall, the feed line may be manufactured using a rotary swagingprocess. Preferably, at least the section of the feed line having thecapillary line section and the transition section adjacent to thecapillary line section are produced by means of a rotary swagingprocess. Particularly preferably, at least the section of the feed linewith the capillary line section and the funnel-shaped transitionsections is produced by means of the rotary swaging process. By usingthe rotary swaging process, it is possible to reliably achieve a highquality with low surface roughness and lower surface waviness of theinside surface of the feed line that determines the flow cross-section.

The wall thickness of the capillary line section may be equal to or lessthan the wall thickness of the feed line section that is adjacent to thetransition section upstream toward the capillary line section. Thisfacilitates the provision of a large space next to the capillary linesection or around the capillary line section for the return of the gasfrom the expansion zone. In addition, the heat transfer between the gasreturned next to or around the capillary line section and the gassupplied through the capillary line section can be increased.

The ratio of the inside diameter of the capillary line section withrespect to the length of the capillary line section is preferablybetween 0.004 at minimum to 0.2 at maximum.

Preferably, the mouth opening of the capillary line section throughwhich the fluid exits from the feed line and enters into the expansionchamber is located on the front side of the capillary line section.Preferably, the jacket of the capillary line section that encloses thelumen of the capillary line section and that conveys the fluid is freeof lateral openings.

The distance between the mouth opening and the opposing wall surface ofthe expansion chamber, said wall delimiting the lumen of the expansionchamber, is preferably between 0.5 mm at minimum and 5 mm at maximum.

BRIEF DESCRIPTION OF TIS DRAWINGS

Further advantageous features of the cryosurgical instrument accordingto the invention can be inferred from the dependent claims, as well asfrom the description hereinafter and the figures. They show in

FIG. 1 —a detail, in longitudinal sectional view, of a distal end of acryosurgical instrument according to prior art,

FIG. 2 a —a detail, in longitudinal sectional view, of an exemplarycryosurgical instrument according to the invention,

FIGS. 2 b to 2 d —views of cross-sections of the instrument according tothe invention depicted in FIG. 2 a , on the section planes shown in FIG.2 a,

FIG. 3 —a detail, in longitudinal sectional view, of an exemplarycryosurgical instrument according to the invention,

FIG. 4 —a detail, in longitudinal sectional view, of a cryosurgicalinstrument according to another exemplary embodiment,

FIG. 5 —a detail, in longitudinal sectional view, of an exemplarycryosurgical instrument according to the invention guided in the workingchannel of an endoscope,

FIG. 6 —a detail, in longitudinal sectional view, of an exemplaryinstrument according to the invention, and

FIG. 7 —a detail, in longitudinal sectional view, of an exemplaryinstrument according to the invention.

DETAILED DESCRIPTION

FIG. 1 is a longitudinal sectional view of a distal end section 13 of aprior-art cryosurgical instrument 10. The instrument 10 has a shaft 11that extends up to a head 12 of the instrument 10 on the distal end 13 aof the instrument 10. Outside, on the head 12, there is provided anadhesion surface 14 where a tissue sample can attach frozen for removal.Inside the shaft 11 there is arranged a feed line 15 for supplying gasto the distal end 13 a of the instrument 10. The feed line 15 ends withan aperture 16 having an opening (mouth) 17, through which the gas mayflow out of the feed line 15 into an expansion chamber 18 in the head 12of the instrument 10. When the gas stream from the feed line 15 isdecelerated at the aperture 16 and the gas expands downstream of theaperture 16 upon entering into the expansion chamber 18, theJoule-Thomson effect will become apparent on the gas in that theexpanded gas in the expansion chamber 18 experiences a temperaturereduction. Consequently, said gas is able to cool off the head 12 of theinstrument 10 having the adhesion surface 14. The cooled gas leaves theexpansion chamber 18 through a return line 19 that is arranged in theshaft 11 next to the feed line 15. The flowback of the gas out of theexpansion chamber 18 into the return line 19 can—as is indicated byarrows in FIG. 1 —be impeded by the gas flowing out of the mouth opening17. Therefore, a relatively large expansion chamber 18 must be providedin order to be able to ensure a suitable backflow.

FIG. 2 a shows a longitudinal section of a cryosurgical instrument 10according to the invention. In the cryosurgical instrument 10 accordingto the invention the distal end 20 of the feed line 15 is formed by acapillary line section (21) (capillary tube section). The capillary linesection 21 has a mouth 22 into the expansion chamber 18 on the frontside 23 of the capillary line section 21. The capillary line section 21extends up to and into the head 12 of the instrument 10 that is formedby a cap 24 that encloses the expansion chamber 18. The distance 25between the mouth opening 22 of the capillary line section 21 and theopposing wall surface 26 of the cap 24 that delimits the expansionchamber 18 is preferably 0.5 mm at minimum up to 5 mm at maximum. Thewall surface 26 of the cap 24 opposite the mouth 22 of the capillarytube section 21, said section delimiting the lumen 27 of the expansionchamber 18, may be—as shown—for example a spherical cap surface 26 thatis disposed and arranged to convey gas impinging on the wall surface 26of the cap 24 into the feedback line 19.

The capillary line section 21 forms the n-th step section 30 n of aseries of at least n=2, preferably n>2, for example, and as shown inFIG. 2 a, n=3 step sections 30 n−2, 30 n−1, 30 n of the feed line 15.Arranged between two step sections 30 n−2, 30 n−1, 30 n of the feed line15, there is respectively one transition section 32 n−2, 32 n−1 adjacentto the two step sections 30 n−2, 30 n−1 or 30 n−1, 30 n, respectively.In at least one transition section 32 n−2, 32 n−1 the insidecross-sectional area 33 of the feed line 15 decreases preferablyfunnel-like, for example conically, in distal direction 34 toward themouth 22 of the capillary line section 21, so that when the instrument10 is loaded with a fluid, for example a gas, an acceleration of thefluid flowing through the feed line 15 toward the mouth 22 will occur inthe transition sections 32 n−2, 32 n−1. The inside wall surface 35 ofthe transition section 32 n−1 adjacent to the capillary tube section 21preferably has essentially no surface sections perpendicular to the flowdirection 34 of the gas, against which the gas flowing through thetransition section in flow direction 34 toward the expansion chamber 18would have to flow. Preferably, the same applies to each of theremaining transition sections 32 n−1. Rather, the depicted exemplarytransition section 32 n−1 toward the capillary tube section 21 has aninside wall surface 35 that is inclined relative to the direction offlow 34—viewed in longitudinal section through the transition section 32n−1—wherein their circumferential sections include acute angles smallerthan 90° with the direction of flow 34. The remaining transitionsections 32 n−2 are preferably configured in the same way. FIG. 2 ashows a funnel-shaped transition section 32 n−2 toward the next to laststep section 30 n−1 and a funnel-shaped transition section 32 n−1 towardthe capillary line section 30 n that forms the last step section 30 n ofthe sequence. Preferably, the flow path tapers continuously in atransition region 36 from before the transition section 32 n−1 to thecapillary line section 30 n, 21, through the transition section 32 n−1in the capillary line section 21. Preferably, there are—in thetransition region 35 in the flow path in the feed line 15—in particularno inside wall surfaces of the feed line 15 perpendicular to thedirection of flow 34 that would lead to an abrupt change of the flowcross-section. Preferably, the flow cross-section of the feed line 15decreases in each transition section 32 n−2, 32 n−1 of the feed line 15between the step sections 30 n−2, 30 n−1, 30 n in a funnel-shaped mannerin the direction of flow 34 in the direction toward the mouth 22, sothat, preferably, a series of alternatingly arranged step sections 30n−2, 30 n−1, 30 n and transition sections 32 n−2, 32 n−1 having afunnel-shaped inside tapering cross-section are formed.

It is advantageous when the flow cross-section in the transitionsection(s) 32 n−2, 32 n−1 of the feed line 15 does not decrease abruptlyfrom the flow cross-section in the step section 30 n−2 or 30 n−1 of thefeed line 15, said step section being arranged in front of thetransition section 32 n−2 or 32 n−1 and being adjacent to the transitionsection 32 n-2 or 32 n−1, toward the flow cross-section in the stepsection 30 n−1 or 30 n of the feed line 15, said section being adjacentto the transition section 32 n−2 or 32 n−1 in the flow path in thetransition section(s) 32 n−2, 32 n−1, but when the flow path in thetransition section(s) 32 n−2, 32 n−1 tapers beyond a path section of theflow path toward the mouth 22. It is this that reduces any eddying ofthe fluid and the pressure fluctuations of the fluid in the step section30 n−1, 30 n of the feed line 15 following the transition section 32 n−2or 32 n−1.

The tapering angle 37 of the inside cross-section 33 in the transitionsection 32 n−1 toward the capillary tube section 21, 30 n is preferably15° at minimum to 40° at maximum. The tapering angle 37 is determined bythe inside wall surface 35 of the transition section 32 n−1 thatlaterally delimits the flow cross-section through the transition section32 n−1. The inside wall surface 35 of the transition sections 32 n−2, 32n−1—viewed in longitudinal section through the feed line 15 along thedirection of flow 34—is preferably arranged inclined with respect to thedirection of flow 34. The inside wall surface 35 may be, for example,the lateral surface of a truncated cone or a truncated pyramid. Thetransition section 32 n−2 toward the next to last step section 30 n−1and/or the transition section 32 n−1 toward the capillary line section21 may be symmetrical relative to a plane parallel to the direction offlow 34. The centers of the flow cross-sectional areas in the transitionsection 32 n−2 toward the next to last step section 30 n−1 and/or thecenters of the flow cross-sectional areas in the transition section 32n−2 in the transition section 32 n−1 on the capillary line section 21can be located—as in a symmetrical funnel—on a straight line thatextends perpendicularly to the flow cross-sectional area in the inlet inthe respective transition section 32 n−1, 32 n−2. As an alternative to asymmetrical funnel-shaped tapering of the flow cross-section in one ormore transition sections 32 n−2, 32 n−1, the flow cross-section of thetransition section 32 n−2 may taper toward the next to last step section30 n−1 and/or the transition section 32 n−1 toward the last step section30 n, for example as in an asymmetrical funnel.

The step sections 30 n−2, 30 n−1, 30 n define the inside cross-sectionalsteps. In a step section 30 n−2, 30 n−1, 30 n, the inside cross-sectionsbelong to an inside cross-sectional step. Inside each step section 30n−2, 30 n−1, 30 n the inside cross-section of the feed line 15 remainswithin a specific size range (step). Within a step section 30 n−1, 30 n,the flow cross-section may be constant, for example. The insidecross-sections in the size range of a step section 30 n−2, 30 n−1 aregreater than the inside cross-sections in the size range of therespectively downstream (toward the mouth) step section 30 n. The feedline 15 displays, accordingly, not a surge-like stepped progression ofthe inside cross-section between the steps in the transition sections 32n−2m 32 n−1, but, preferably displays a continuous or step-by-steptransition of the flow cross-section to the next step. It is alsopossible that the flow cross-section tapers step-by-step in at least inone transition section 32 n−2, 32 n−1 in at least one first longitudinalsection of the transition section 32 n−2, 32 n−1 and continuously in atleast one other longitudinal section of the transition section 32 n−2,32 n−1 that is located upstream or downstream of the first longitudinalsection, so that the flow cross-section in the transition section 32n−2, 32 n−1 overall tapers continuously and step-by-step toward the nextstep. In particular, the feed line 15 may be configured in such a mannerthat the inside cross-section of the feed line 15 decreases monotonouslyfrom the start of the series of step sections 30 n−2, 30 n−1, 30 n inthe direction of flow 34 up to the mouth 22 of the feed line 15. Thismeans that the inside cross-section decreases—at least in somesections—strictly monotonously and may optionally remain the same insome sections.

In one embodiment, the inside wall surface 35 of the feed line 15 in thetransition section 30 n−1 toward the capillary line section 21, into thecapillary line section 21 up to the mouth of the feed line 15, may befree of edges or bends oriented transversely with respect to thedirection of flow 34 through the feed line 15, said edges or bendspotentially meaning an abrupt change of the gradient of the flowcross-section of the feed line 15.

Next to the feed line 15 and/or around the feed line 15, there ispreferably formed the flow cross-section of the return line 19. In thedepicted exemplary embodiment, the feed line 15 is arranged, at least insome sections, in the return line 19. The flow cross-section of thereturn line 19 is delimited, on the one hand, by the wall 38 a of theshaft as well as the wall 38 b of the head 12, and on the other hand, bythe wall 39 of the feed line 15. In FIG. 2 a , the feed line 15 is shownas being arranged coaxially in the shaft 11 and the cap 24. However, thefeed line 15, as well as the shaft 11 and/or the cap 24, may benon-coaxial, i.e., preferably have parallel center axes.

Preferably, the outside cross-section 40 of the feed line 15 in thetransition sections 32 n−2, 32 n−1, as illustrated, does not decreaseabruptly in the direction 34 toward the mouth 22 but, preferably,continuously or step-by-step. In at least one transition section 32 n−2,32 n−1 the outside cross-section of the feed line 15 may decreasecontinuously in longitudinal sections and step-by-step in longitudinalsections—in the direction toward the mouth 22. As a result of this, theflow cross-section 41 of the return line 19—as shown by the exemplaryembodiment according to FIG. 2 a — can decrease in the transitionsections 32 n−2, 32 n−1 in the direction 42 of the gas flowing from theexpansion chamber 18 through the return line 19, respectively along thelength of the transition sections, i.e., not abruptly from the flowcross-section ahead of the transition section 32 n−2, 32 n−1 to the flowcross-section after this transition section 32 n−2, 32 n−1. The flowcross-section 41 of the return line 19 may decrease, in particular,continuously or step—by—step, or, in longitudinal sections, continuouslyand—in the direction of flow 42 of the gas flowing away from theexpansion chamber 18 in the transition sections 32 n−2, 32 n−1, inparticular—in a continuous or step-by-step manner, or continuously inlongitudinal sections and step-by step in longitudinal sections. Theflow cross-section 41 of the return line 19 next to the capillary tubesection 21, 30 n or around the capillary tube section 21, 30 n and/orbetween the transition sections 32 n−2, 32 n−1 may largely be constant.

Preferably, the step sections 30 n−2, 30 n−1, 30 n determine the outsidecross-section steps. In one step section 30 n−2, 30 n−1, 30 n theoutside cross-sections (outside cross-sectional areas) of the feed line15 belong to one outside cross-section step. Within each step section,the outside cross-section of the feed line remains within a specificsize range (step). Along one step section 30 n−2, 30 n−1, 30 n theoutside cross-sections of the step section 30 n−2, 30 n−1, 30 n, may beconstant, for example. The outside cross-sections in the size range ofone step section 30 n−2, 30 n−1 are greater than the outsidecross-sections in the size range of the respectively downstream (towardthe mouth) following step section 30 n−1, 30 n. Accordingly, the feedline 15 shows preferably a stepped progression of the outsidecross-section displaying—between the steps in the transition sections 32n−2, 32 n−1—a non-abrupt transition of the outside cross-section towardthe next step. Rather, the transition extends preferably over the lengthof the transition section 32 n−2, 32 n−1 and/or the transition of theoutside cross-section toward the next step is preferably continuous, oroccurs—viewed from the flowing fluid—step-by-step. The outsidecross-section of the feed line 15 between the transition sections 32n−2, 32 n−1 shown by FIG. 2 c and between the transition section 32 n−1toward the capillary line section 21 and the mouth 22 is preferablymostly constant, so that the capillary line section 21 displays alargely constant outside cross-section along the longitudinal extent ofthe capillary line section 21.

As can be seen with reference to FIGS. 2 b to 2 d , referring to theexemplary embodiment depicted by FIG. 2 a , the ratio of the flowcross-sectional area content 41 (An−2, An−1, An) of the return line 19next to a step section 30 n−2, 30 n−1, 30 n or around a step section 30n−2, 30 n−1, 30 n increases—due to the formation of the feed line 15 inthe shaft 11—toward the inside cross-sectional area content 33 (Bn−2,Bn−1, Bn) in the step section 30 in the direction of flow 34 toward themouth 22 from step section to step section, meaning that said ratio isgreatest in the capillary line section 21. Thus, analogously,An:Bn≥An−1:Bn−1≥An−2:Bn−2, applies.

The ratio of the area content of the flow cross-section of the returnline 19 next to the capillary line section 21 and/or around thecapillary line section 21 with respect to the area content of the flowcross-section of the capillary line section 21 is preferably greaterthan or equal to 5. The inside diameter 28 (for purposes of clarity,drawn in an exemplary manner in FIG. 3 ) of the capillary line sectiondetermines the flow cross-section 33 of the capillary line section. Theratio of the inside diameter 28 of the capillary line section 21 withrespect to the length (for purposes of clarity, drawn in an exemplarymanner in FIG. 3 ) of the capillary line section 21 is preferablybetween 0.004 at minimum and 0.2 at maximum. The length 29 of thecapillary tube that forms the capillary line section 21 may be, forexample between 1 mm at minimum and 15 mm at maximum. The insidediameter 28 of the capillary line section 21 may be, for example, 60micrometers at minimum and 200 micrometers at maximum.

The section of the feed line 15 having the transition sections 32 n−2,32 n−1, the step section 30 n−1 between the transition sections 32 n−2,32 n−1 and the capillary line section 21, 30 n is preferably formedwithout seams in one piece. For example, the section can be made byusing the rotary swaging process. The cap 24 of the shaft forming thehead 12 having the adhesion surface 14 may consist of stainless steel,for example. For example, the shaft 11 may consist of PEEK, PA, PUR orPTFE. The shaft 11 may be rigid or flexible.

During operation of the cryosurgical instrument 10, the following takesplace:

With the use of a fluid source (not illustrated) connected to the feedline 15, the feed line 15 is loaded with a fluid, in particular gas, forexample N₂O or CO₂, in which case the fluid flows on the distal workingend 43 of the cryosurgical instrument 10 from a tube-shaped step section30 n−2, 30 n−1, 30 n through the adjacent transition section 32 n−2, 32n−1 in the direction of the mouth 22 and the expansion chamber 18 intothe subsequent tube-shaped step section 30 n−2, 30 n−1, 30 n. Due to thefunnel-like decrease of the inside cross-section 33 and thus the flowcross-section of the feed line 15 in the transition sections 32 n−2, 32n−1 in the direction of the expansion chamber 18, the fluid isaccelerated in the transition sections 32 n−2, 32 n−1. Due to thereduction that is not abrupt in the transition sections but—extendingover a certain length—preferably continuous or step by step of the flowcross-section 33 from step to step, eddying and/or pressure fluctuationsin the step section 32 n−2, 32 n−1 due to accelerations in eachtransition section 32 n−2, 32 n−1 are largely prevented. Preferably, thestep sections 30 n−2, 30 n−1, 30 n each have one length, so that eddiesand/or pressure fluctuations in step the section 30 n−2, 30 n−1, 30 nfollowing the transition section 32 n−2, 32 n−1 abate largely orcompletely. The gas flows from the (n−1)st step section through the(n−1)st transition section into the capillary tube section 21 (nth stepsection). Potential pressure fluctuations in the gas due to thetransition from the (n−1)st step section to the capillary tube section21 preferably abate completely due to the formation of the capillarytube section 21. In the capillary tube section 21, there results alaminar flow in the direction of flow 34 toward the mouth 22 exhibitingthe corresponding velocity profile that—due to the abating of thepressure fluctuations in the capillary tube section 21 in the distal endsection of the capillary tube section 21 adjacent to the mouth opening22 preferably does no longer change in the direction of flow 34(undisturbed flow profile). The capillary tube section 21 forms theaperture for the gas for the formation of the Joule-Thomson effect.Therefore, an aperture 16—as in prior art according to FIG. 1 —thatresults in a large widening of the fluid jet when flowing out of thefeed line 15 into the expansion chamber 18 and thus leads to a stronginteraction with the flowing back gas can thus be omitted as illustratedby FIG. 2 a . The gas stream flows out of the capillary tube section 21into the expansion chamber 18 and, due to the acceleration in thetransition sections 32 n−2, 32 n−1 and the absence of pressurefluctuations before flowing out of the mouth 22, far into the expansionchamber 18 in the direction of the opposing wall surface 26 of theinstrument head 12. In doing so, the gas flows out of the mouth 22largely unimpeded by the flowing back gas. The gas that flows out of themouth 22 and expands in the expansion chamber 18 experiences atemperature reduction as a result of the Joule-Thomson effect and coolsdown the head 12 and the adhesion surface 14 in such a manner that atissue sample can freeze to the adhesion surface 14. Thereafter, thetissue sample can be separated and removed from the remaining tissue bypulling the instrument 10.

Accordingly, the backflow of the cooled gas is not impeded by theout-flowing gas. The expanded gas from the expansion chamber ratherpreferably flows parallel to the fluid leaving the feed line 21 throughthe mouth opening 22 into the expansion chamber 18 in the opposite senseof flow direction out of the expansion chamber 18 into the return line19. This large-volume back flow is illustrated by arrows in FIG. 3 thatshows a detail of the instrument 10 on its distal end 13 a. The gasflowing back through the return line 19 slides past the outside wallsurface of the capillary tube section 21 of the feed line 15 andwithdraws heat from the gas flowing through the capillary line section21. This is promoted in that the wall 44 of the capillary tube section21 is preferably as thin as the wall of the step section 30 n−1 that isadjacent to the transition section 32 n−1 toward the capillary tubesection 21, or even thinner.

The backflowing gas may escape through lateral openings (not shown) inthe shaft 11, for example.

FIG. 4 shows a detail of a modified exemplary embodiment of theinstrument 10 according to the invention. Shown is an end section 13 ofthe instrument 10.

The feed line 15 and the return line 19 are formed next to each other inthe shaft 11 of the instrument 10. The capillary tube section 21 of thefeed line 15 is inserted in the section of the feed line 15 provided inthe shaft 11. The capillary tube section 21 reaches into the cap 24 ofthe instrument 10, said cap enclosing the expansion chamber 18.

The feed line 15 has at least three step sections 30 n−2, 30 n−1, 30 n,wherein the last step section 30 n is formed by the capillary tubesection 21. At least in the transition section 32 n−2 on the next tolast step section 30 n−1, the inside cross-section of the feed line 15decreases in a funnel-shaped manner in the direction toward the mouth 22in the expansion chamber 18 in the shape of a funnel.

The flow cross-section of the return line 19 connected to the expansionchamber 18 in the shaft 11 decreases in the transition sections 19 m−2,19 m−1 of the return line 19 in the form of a funnel. Between thetransition sections 19 m−2, 19 m−1 of the return line 19, the flowcross-section in the return line 19 is preferably largely constant. Thenumber of transition sections 19 m−2, 19 m−1 of the return line 19 maycorrespond to the number of transition sections 32 n−3, 32 n−2, 32 n−1in the feed line 15.

FIG. 5 shows a cryosurgical instrument 10 according to the inventionwhose shaft 11 is movably guided in longitudinal direction in a workingchannel 45 of an endoscope 46. On the distal end of the shaft 11 of theinstrument 10, the head 12 of the instrument 10 is arranged with a slimdistal end section 47, in which case the outside diameter 48 of the endsection 47 is reduced relative to the outside diameter 49 of the shaftsection adjacent to the head 12. The capillary tube section 21 extends,in the narrow end section 47, into the expansion chamber 18, saidchamber being delimited by the end section 47. In the exemplaryembodiment, the fluid is accelerated in at least two successivetransition sections 32 n−2, 32 n−1 of the feed line 15 with respectivelyfunnel-shaped reductions of the inside cross-section 33 in the directionof flow 34 toward the mouth 22 in the expansion chamber 18, in whichcase a tube-shaped step section 30 n−1, 30 n follows each transitionsection 32 n−2, 32 n−1. The distally last step section 30 n is thecapillary tube section 21. Due to the uniform acceleration in thetransition sections 32 n−2, 32n−1 and due to the abatement of pressurefluctuations in the capillary tube section 21—so that the flow profileof the fluid flowing through the feed line 15 is preferably constant atthe end of the capillary tube section 21, i.e., does no longer change inthe direction of flow 34—the fluid will flow, after leaving the mouth22, far into the expansion chamber 18. As a result of this, a suitablereturn of the expanded gas out of the expansion chamber 18 withoutimpediment due to the gas flowing out of the mouth 22 into the expansionchamber 18 is possible, despite the confined spatial conditions due tothe slim end section 47 of the instrument head 12. Now a tissue sample50 can be taken with the instrument head 12, said sample having adiameter that is smaller than the diameter of the working channel 45 ofthe endoscope 46. Consequently, the head 12 of the instrument 10 withthe tissue sample 50 can be retracted into the working channel 45 of theendoscope, i.e., after the tissue sample 50 has been taken, so that thetissue sample 50 in the working channel 45 of the endoscope 46 can beremoved in a protected manner from the body of the patient.

FIG. 6 shows a detail of an instrument 10 according to the inventionwith a head that can be mounted with a tube-shaped mounting section 51to the shaft 11 of the instrument 10. The head 12 has a pointed endsection 52, and, between the end section 52 and the mounting section 51,there is arranged a tube-shaped adhesion section 53. The head 12 has awaist 54 on the adhesion section 53. In particular, the outside diameterof the adhesion section 53 is reduced relative to the outside diameterof the pointed end section 52. Preferably, the wall of the adhesionsection 53 displays a reduced thickness compared to the wall of themounting section 51. The adhesion section 53 delimits the expansionchamber 18 that may extend up into the pointed end section 52. Thecapillary line section 21 of the feed line 15 extends into the adhesionsection 53. The pointed end section 52 facilitates the puncturing thetissue for taking the sample. For taking the sample, the feed line 15 ofthe instrument 10 is loaded with fluid, in which case the fluid flowsthrough the feed line 15 in the direction of flow toward the expansionchamber 18 and expands in the expansion chamber and cools the head 12.In doing so, the freezing effect on the tissue may originate from theadhesion section 53, in particular. The taking of the sample issimplified because, due to the reduced outside diameter of the adhesionsection 53 compared to the outside diameter of the pointed end section52, there is formed a positive connection between the head 12 and thefrozen, attached tissue.

FIG. 7 shows a detail of the distal end 13 of an exemplary embodiment ofthe instrument 10 according to the invention with a head 12 that ismounted to the shaft 11 by means of a head-receiving part 55. Thehead-receiving part 55 of the instrument 10 extends inside the lumenthat is enclosed by the shaft 11 and the head 12. The outside diameterof the capillary line section 21 is smaller than the outside diameter ofthe step section 30 n−1 adjacent to the transition section 32 n−1 towardthe capillary line section 21. Due to the continuous tapering of theinside cross-section of the feed line 15 in the transition section 32n−1 toward the capillary line section 21, an impediment of the backflowof the expanded gas by the fluid flowing out of the feed line 15 islargely prevented. In addition, the flow resistance of the return line19 can be improved due to the continuous increase of the outsidecross-section 40 of the feed line 15 in the transition section 32 n−1(in the direction of flow of the gas flowing away from the expansionchamber 18) compared to an instrument with abrupt increase. Due to theconfiguration of the feed line 15, thus—despite the reduction of thefree volume through the head-receiving part 55—a suitable return of theexpanded gas is made possible. The wall surface 26 opposite the mouth 22of the capillary tube section 21 and delimiting the expansion chamber 18is the lateral surface of a cone—in this exemplary embodiment and alsoin the embodiment according to FIG. 6 .

Disclosed herein is a cryosurgical instrument 10 that comprises a feedline 15 for conveying fluid into an expansion chamber 18 of theinstrument 10. The feed line 15 has a capillary line section 21 thatterminates in the expansion chamber 18 and that forms an aperture forthe fluid to form the Joule-Thomson effect during the expansion of thefluid in the expansion chamber 18. The flow cross-section of the feedline 15 decreases in at least one transition section 32 n−2, 32 n−1,preferably in two or more transition sections 32 n−2, 32 n−1, of thefeed line 15 in the form of a funnel in the direction of flow 34 towardthe expansion chamber 18. Following each transition section 32 n−2, 32n−1—viewed in the direction of flow 34—there preferably follows,adjacent to the transition section 32 n−2, 32 n−1, a step section 30n−1, 30 n of the feed line 15, in which latter section the flowcross-section is preferably largely constant. The last step section 30n−1, 30 n is preferably formed by the capillary line section 21.Pressure fluctuations in the fluid can abate in the step sections 30n−1, 30 n. Due to the acceleration of the fluid in the transitionsections 32 n−2, 32 n−1 and due to the abating of pressure fluctuationsin the capillary tube section 21 and, optionally in the additional stepsections 30 n−1, 30 n−2, the expansion range in the expansion chamber 18is increased, without impeding the backflow of the expanded gas out ofthe expansion chamber 18.

Due to the use of the capillary tube section 21, as well as thefunnel-shaped transition section(s) 30 n−2, 30 n−1, the free path lengthof the fluid jet is greatly increased without widening the fluid jet inthe instrument 10 according to the invention compared to a cryosurgicalinstrument having an aperture at the end of the feedback line 15, sothat the interaction between the fluid flowing from the mouth opening 22away into the expansion chamber 18 and the gas flowing back from theexpansion chamber 18 can be greatly reduced. Preferably, the pressurefluctuations and/or eddies of the fluid flowing through the feed line 15in the direction toward the mouth 22 abate in one embodiment of theinstrument 10 according to the invention in the capillary tube section21 to such an extent that they no longer define the free path length ofthe fluid jet without widening in the expansion chamber 18. The freepath length of the fluid jet without widening is measured from the mouthopening 22 in the direction of flow 34 of the fluid up to the point inthe expansion chamber 18 at which the fluid jet diameter exceeds a sizethat is equal to the size of the outside diameter of the capillary linesection 21 at the mouth opening 22, or the free path length of the fluidjet without widening is measured from the mouth opening 22 in thedirection of flow 34 of the fluid up to the point in the expansionchamber 18 at the level (in flow direction 34) where an interaction ofthe fluid jet flowing away from the mouth opening 22 into the expansionchamber 18 with the gas flowing back to the feedback line 19 sets in.

LIST OF REFERENCE SIGNS

10 Instrument 11 Shaft 12 Head 13 Distal end section of the instrument13a Distal end of the instrument 14 Adhesion surface 15 Feed line 16Aperture 17 Opening 18 Expansion chamber 19 Return line 19m−2, 19m−1Transition sections of the return line 20 Distal end of the return line21 Capillary line section/capillary tube section 22 Mouth 23 Front side24 Cap 25 Distance 26 Wall surface 27 Lumen 28 Diameter 29 Length 30n−2,30n−1, Step section 30n 32n−2, 32n−1 Transition section 33 Insidecross-sectional area/flow cross-sectional area 34 Direction of flowtoward the expansion chamber 35 Inside wall surface 36 Transition region37 Tapering angle 38a Wall of the shaft 38b Wall of the head 39 Wall ofthe feed line 40 Outside cross-section 41 Flow cross-section of thereturn line 42 Direction of flow away from the expansion chamber 43Distal working end 44 Wall of the capillary tube section 45 Workingchannel 46 Endoscope 47 End section 48 Outside diameter of the endsection 49 Outside diameter of the shaft 50 Tissue sample 51 Mountingsection 52 End section 53 Adhesion section 54 Waist 55 Head-receivingpart An−2, An−1, Flow cross-sectional area content of the return line AnBn−2, Bn−1, Flow cross-sectional area content of the feed line Bn S₁-S₁,S₂-S₂, Section planes S₃-S₃

What is claimed is:
 1. A cryosurgical instrument, comprising: a hollowshaft including a closed distal end with an outer adhesion surface forharvesting a tissue sample thereon and an expansion chamber disposedwithin the hollow shaft at the closed distal end thereof; and a feedline disposed within the shaft for supplying a fluid into the expansionchamber, wherein the feed line has a capillary line section that extendsalong a longitudinal axis to a distal end of the feed line, wherein thedistal end of the feed line is spaced from the closed distal end of thehollow shaft and terminates at a mouth opening disposed at an endmostdistal extent of the feed line in the expansion chamber, wherein themouth opening is spaced from the closed distal end of the hollow shaftand is oriented axially for supplying fluid distally into the expansionchamber; wherein an inside diameter of the capillary line section isless than or equal to 200 μm.
 2. The cryosurgical instrument of claim 1,further comprising a return line disposed within the hollow shaft andfluidically connected to the expansion chamber for returning fluid outof the expansion chamber, wherein the return line is disposed entirelywithin the hollow shaft and extends around or adjacent to the feed linein a direction away from the expansion chamber for returning fluid outof the expansion chamber.
 3. The cryosurgical instrument according toclaim 2, wherein the return line is defined by an exterior surface ofthe feed line and an interior surface of the hollow shaft.
 4. Thecryosurgical instrument according to claim 2, wherein the feed line isarranged in or next to the return line, wherein a ratio of a flowcross-section of the return line with respect to an interiorcross-section of the capillary line section is greater than or equal to5.
 5. The cryosurgical instrument of claim 1, wherein a ratio of theinside diameter of the capillary line section with respect to a lengthof the capillary line section is between a minimum of 0.004 up to amaximum of 0.2.
 6. The cryosurgical instrument according to claim 1,wherein a distance between the mouth opening and an opposite wallsurface of the expansion chamber ranges from 0.5 millimeters to 5millimeters.
 7. The cryosurgical instrument according to claim 1,wherein a length of the capillary line section ranges from 1 millimeterto 15 millimeters.
 8. The cryosurgical instrument according to claim 1,wherein the feed line has a first section and a second section proximalto the capillary line section with different-size interiorcross-sections and a tapered transition section from the first sectionto the second section in a direction of flow of the fluid toward theexpansion chamber.
 9. A cryosurgical instrument, comprising: a hollowshaft including a closed distal end with an outer adhesion surface forharvesting a tissue sample thereon and an expansion chamber disposedwithin the hollow shaft at the closed distal end thereof; and a feedline disposed within the shaft for supplying a fluid into the expansionchamber, wherein the feed line has a capillary line section that extendsalong a longitudinal axis to a distal end of the feed line, wherein thedistal end of the feed line is spaced from the closed distal end of thehollow shaft and terminates at a mouth opening disposed at an endmostdistal extent of the feed line in the expansion chamber, wherein themouth opening is spaced from the closed distal end of the hollow shaftand is oriented axially for supplying fluid distally into the expansionchamber; wherein a ratio of an inside diameter of the capillary linesection with respect to a length of the capillary line section isbetween a minimum of 0.004 up to a maximum of 0.2.
 10. The cryosurgicalinstrument of claim 9, further comprising a return line disposed withinthe hollow shaft and fluidically connected to the expansion chamber forreturning fluid out of the expansion chamber, wherein the return line isdisposed entirely within the hollow shaft and extends around or adjacentto the feed line in a direction away from the expansion chamber forreturning fluid out of the expansion chamber.
 11. The cryosurgicalinstrument according to claim 10, wherein the return line is defined byan exterior surface of the feed line and an interior surface of thehollow shaft.
 12. The cryosurgical instrument according to claim 10,wherein the feed line is arranged in or next to the return line, whereina ratio of a flow cross-section of the return line with respect to aninterior cross-section of the capillary line section is greater than orequal to
 5. 13. The cryosurgical instrument according to claim 9,wherein a distance between the mouth opening and an opposite wallsurface of the expansion chamber ranges from 0.5 millimeters to 5millimeters.
 14. The cryosurgical instrument according to claim 9,wherein a length of the capillary line section ranges from 1 millimeterto 15 millimeters.
 15. The cryosurgical instrument according to claim 9,wherein the feed line has a first section and a second section proximalto the capillary line section with different-size interiorcross-sections and a tapered transition section from the first sectionto the second section in a direction of flow of the fluid toward theexpansion chamber.
 16. A cryosurgical instrument, comprising: a hollowshaft terminating at a distal end; a head receiving member having aproximal portion received in the distal end of the hollow shaft and adistal end portion; a head member disposed on the distal end portion ofthe head receiving member, the head member including a closed distal enddefining an expansion chamber and an outer adhesion surface forharvesting a tissue sample thereon; and a feed line disposed within thehollow shaft for supplying a fluid into the expansion chamber, whereinthe feed line has a capillary line section that extends along alongitudinal axis to a distal end of the feed line, wherein the distalend of the capillary line section is spaced from the closed distal endof the head member and terminates at a mouth opening disposed at anendmost distal extent of the capillary line section, wherein the mouthopening is spaced from the closed distal end of the head member and isoriented axially for supplying fluid distally into the expansionchamber.
 17. The cryosurgical instrument of claim 16, wherein the feedline tapers gradually from a proximal section to the capillary linesection, wherein the proximal section has a larger interiorcross-sectional area than an interior cross-sectional area of thecapillary line section, wherein the proximal section is positionedproximal to the proximal portion of the head receiving member.
 18. Thecryosurgical instrument of claim 16, wherein an inside diameter of thecapillary line section is less than or equal to 200 μm.
 19. Thecryosurgical instrument of claim 16, wherein the head member includes acone-shaped interior surface that defines at least a portion of theexpansion chamber.
 20. The cryosurgical instrument of claim 16, wherein,further comprising a return line disposed within the hollow shaft andfluidically connected to the expansion chamber for returning fluid outof the expansion chamber, wherein the return line extends around oradjacent to the feed line in a direction away from the expansion chamberfor returning fluid out of the expansion chamber.